This application relates to a scroll compressor, wherein a back pressure chamber is provided with a large cavity to reduce the start-up load on the motor. The large cavity must be filled with pressurized fluid as the compressor starts up before the scroll members can move into engagement with each other.
Scroll compressors have become widely utilized in refrigerant compression applications. In a typical scroll compressor, a first scroll member includes a base with a generally spiral wrap extending from the base. A second scroll member also has a base and a generally spiral wrap extending from its base. The two wraps interfit to define compression chambers. One of the two scroll members is caused to orbit relative to the other, and as they orbit, the size of the compression chambers is decreased, compressing an entrapped refrigerant.
A separating force is created by the compressed refrigerant that tends to push the two scroll members away from each other. To entrap and define a compression chamber, the wrap of each scroll member must be in contact with the base of the other scroll member. The separating force tends to move the wraps out of engagement, and thus prevents compression.
To address this separating force, scroll compressors have utilized a back pressure chamber defined behind the base of one of the two scroll members. A compressed refrigerant is tapped into this chamber, and creates a force tending to hold the two scroll members in contact with each other.
One challenge with scroll compressors is that at start-up the motor must begin to drive a shaft to cause the scroll member to orbit. At start-up, the load on this motor to begin the rotation of the shaft is relatively large. It would be desirable to reduce this start-up load.